Presentation on theme: "Introduction to(GMAW) Gas Metal Arc Welding"— Presentation transcript:
1 Introduction to(GMAW) Gas Metal Arc Welding GMAW Unit 1 Lesson 1Objective: Demonstrate proper setup and maintenance of GMAW equipment.
2 GMAW ProcessGas Metal Arc Welding (GMAW) uses an electric arc to melt a consumable wire electrode and fuse it with the base metal. The arc generates an intense heat of 6,000 to 10,000 degrees Fahrenheit. The process normally operates with direct current electrode positive (DCEP).
3 GMAW EquipmentThe wire electrode is fed by the wire feeder through the gun cable to the welding gun.The electric current is transferred from the power source through the gun cable and to the contact tip.The contact tip conducts the electric current to the wire electrode.The gun cable also transports the shielding gas to through the gas diffuser and out the nozzle.The welding arc is stabilized and the molten filler and base metal are protected from oxidation by the shielding gas.
4 7E2DA225-EFBF-A940-81C4-A9BDFE28FAFF What does the abbreviationGMAW stand for?iRespond QuestionMultiple ChoiceF7E2DA225-EFBF-A940-81C4-A9BDFE28FAFFA.) Gas Machine Arc WeldingB.) Gas Metal Arc WeldingC.) Gas Material Arc WeldingD.) Gas Method Arc WeldingE.)
5 In a GMAW system, how is the electric current transferred to the electrode? iRespond QuestionMultiple ChoiceFD23B A-DE41-B8EA-42AC4DE0838FA.) Through the gun cable and linerB.) Through the contact tubeC.) Through the wire feed rollsD.) Through the gas diffuserE.)
6 Process Setup GMAW machines can come in 2 types. The most common being the power source and wire feeder in one unit.The second type is when the power source and wire feeder are separate machines connected to each other.Regardless of the machine type. The GMAW process has two main controls.Wire speed- controls the amperage or heatVoltage- controls the arc gap
7 Power suppliesThe basic power supply used for GMAW is designed for the process. It is called a Constant Potential (CP) or more commonly Constant Voltage (CV). The Arc gap is controlled by the machine voltage. CV machines maintain a constant voltage by varying the amperage to maintain a consistent arc gap.
9 What type of Power source is used for GMAW? iRespond QuestionMultiple ChoiceF276703BA-4D27-F E00D CA.) Constant CurrentB.) Alternating CurrentC.) Variable VoltageD.) Constant VoltageE.)
10 GMAW Modes of Metal Transfer There are 3 basic types of metal transfer associated with GMAW.Short Circuit TransferGlobular TransferSpray Transfer
11 Short Circuit Transfer Commonly referred to as short arc, this is probably the most widely used method of metal transfer. As the wire electrode touches the base metal a short circuit is created causing the electrode to melt through and deposit molten metal into the weld joint.There are advantages and disadvantages to the short arc transfer mode.Advantages:Low heat inputWelds in all positionsWelds thin gauge materialsCan be used to bridge gaps in some weld jointsDisadvantages:Small diameter wire, expensive.SpatterCold starts, can cause cold lap on restarts.Limited to materials 1/8” thick or less.
13 Which of the following is an advantage with Short Circuit mode of metal Transfer? iRespond QuestionMultiple ChoiceF89BED4F8-A B479-F798F183D6EFA.) Small diameter wire, expensive.B.) SpatterC.) Cold starts, can cause cold lap on restarts.D.) Welds in all positionsE.)
14 Globular TransferThe globular mode of metal transfer happens when the electrode melts and burns off before touching the base metal. Forming a molten droplet falls and then melts to the base metal.Advantages:High deposition rateHigh quality welds are possibleGood penetration at high speedsDisadvantages:Considerable amount of smoke and spatterRough weld appearanceCan only be used in the flat position
16 Which of the following is a disadvantage Globular mode of metal Transfer? iRespond QuestionMultiple ChoiceF34B6051B-3FD8-104A-BEEE-DB683485D71EA.) High deposition rateB.) Can only be used in the flat positionC.) High quality welds are possibleD.) Good penetration at high speedsE.)
17 Spray-Arc TransferSpray-Arc often called Spray Transfer is a metal transfer mode where the electrode is fed into the weld zone and melted off above the base metal. Electromotive force propels the molten electrode to the base metal.Advantages:Very little or no spatterHigh quality weldsHigh metal depositionFaster welding speedsDeep penetrationDisadvantages:Very large weld poolVery fluid weld poolCan only be used in the flat position when making groove weldsCan only be used in the flat and horizontal position when making fillet welds
19 Modes of TransferTransitions from Short Circuit - Globular arc - Spray arc
20 Which of the following is a disadvantage spray-Arc mode of Transfer? iRespond QuestionMultiple ChoiceF405363A9-51D3-4F4B D027B960B1A.) High quality weldsB.) High metal depositionC.) Faster welding speedsD.) Can only be used in the flat and horizontal position when making fillet weldsE.)
21 Pulsed Spray TransferA variation to the spray transfer process, pulsed spray is a method of pulsing the current forcing a drop of filler material from the end of the electrode at controlled time in the welding cycle.Advantages:Greater metal deposition at lower amperage levels.Decreased warpage is possibleDecreased need for jigs or weld toolingAll positionsDisadvantages:Need for special power suppliesRequires special gas mixtures